New custom games and custom rules screen (#464)

* New waves and limited respawning option.

Added ability to manipulate number of respawns per wave. Added option to hold counting for next wave until all enemies are destroyed

* Critical bug fixed

Fixed frozen wave timer when rules.waitForWaveToEnd was enabled

* Requested changes

* Missed Import

* New custom game and custom rules screen

RulePreset is now a Gamemode (because each of them has a different goal).
New button under Gamemode selection which opens a dialog to modify rules of gamemode.
Now without any mutually exclusive options

* Requested changes

* Applied some text sugestions

* Wrong waveInProgress message displaying fixed

* Unwanted text

* Text changes

* I broke git

* Fixed chrash

* More fixes

New rule : manyCores; needed for sanbox mode

* Visual fix

* Requested changes #1 : small oversights

* Moved respawning logic to Player

and another imports cleanup

* manyCores in now attackMode

* UI changes

* Given back waves to sandbox and integer input in custom rules

* Renamed functions in CustomRulesScreen

* SPACES... Actually one space...

core/src/io/anuke/mindustry/entities/type/Player.java

@@ -54,6 +54,7 @@ public class Player extends Unit implements BuilderTrait, ShooterTrait{
     public Color color = new Color();
     public Mech mech;
     public SpawnerTrait spawner, lastSpawner;
+    public int respawns;
 
     public NetConnection con;
     public boolean isLocal = false;
@@ -103,6 +104,9 @@ public class Player extends Unit implements BuilderTrait, ShooterTrait{
     public void onRespawn(Tile tile){
         boostHeat = 1f;
         achievedFlight = true;
+        if(state.rules.limitedRespawns){
+            respawns--;
+        }
     }
 
     @Override
@@ -489,7 +493,6 @@ public class Player extends Unit implements BuilderTrait, ShooterTrait{
 
     @Override
     public void update(){
-
         hitTime -= Time.delta();
 
         if(Float.isNaN(x) || Float.isNaN(y)){
@@ -516,7 +519,9 @@ public class Player extends Unit implements BuilderTrait, ShooterTrait{
         if(isDead()){
             isBoosting = false;
             boostHeat = 0f;
-            updateRespawning();
+            if(respawns!=0){
+                updateRespawning();
+            }
             return;
         }else{
             spawner = null;
@@ -777,6 +782,7 @@ public class Player extends Unit implements BuilderTrait, ShooterTrait{
         boostHeat = drownTime = hitTime = 0f;
         mech = getStarterMech();
         placeQueue.clear();
+        respawns = state.rules.respawns;
     }
 
     public Mech getStarterMech(){